In the past ten years, Acceptance and Commitment Therapy (ACT) has not only established itself as an effective psychotherapeutic treatment method, but it has also been further developed and refined. The result is a significant advancement in concepts, techniques, and experiential insights. The authors of this book have identified six key processes of ACT, all of which revolve around a central concern: psychological flexibility. This model of psychological flexibility represents another innovative step for ACT, as it can be applied to a wide range of psychological disorders. Hayes, Strosahl, and Wilson clearly explain the fundamentals, procedures, and important aspects of implementation using case examples. This revised new edition of the foundational work on ACT is presented here in a completely new translation.